Socheat said that both sides used rocket launchers, machine guns and rifles in the clash.

"Cambodian soldiers fired with assault rifles at Thailand first and now they started to shell us with artillery and we took appropriate retaliation," General Prawit Wongsuwon, the Thai defence minister, told the AFP news agency.

Phay Siphan, a Cambodian government spokesman, termed the clash an "invasion" of Cambodian territory by Thailand.

Serm Chainarong, the governor of Surin, said authorities there were preparing to evacuate about 5,000 people.

Pich Sokhin, the governor of Cambodia's Oddar Meanchey province, said clashes erupted at around 06:30am (11:30 GMT) in areas around the Ta Moan and Ta Krabei temples, and that the Thais had started firing first.

Soured ties

Thailand and Cambodia regularly accuse each other of starting border fighting.

The Thai-Cambodia border has never been fully demarcated, partly because it is littered with landmines left over from decades of war in Cambodia.

A festering dispute between the two countries over land near a different temple erupted into four days of fighting in February, leaving at least 10 people dead and prompting a UN appeal for a lasting ceasefire.

"It is a very similar situation to other times we've seen such skirmishes. It's very difficult to tell who fired first on these occasions," Al Jazeera's Wayne Hay reported from Bangkok.

"The Thais say that the Cambodians came too close to the disputed border ... in Surin, the Cambodians say that Thai soldier actually crept across that disputed border into Cambodian territory."

Thailand and Cambodia each accused the other of starting those clashes, which erupted around the 900-year-old Hindu temple of Preah Vihear.

Ties between the neighbours have been strained since Preah Vihear was granted UN World Heritage status in July 2008.

The World Court ruled in 1962 that the temple belonged to Cambodia, but both countries claim ownership of a 4.6sq km surrounding area.

Observers say the temple dispute has been used as a rallying point to stir nationalist sentiment in Thailand and Cambodia.

"There are many parts of this border ... that are disputed between the two countries," our correspondent said.

"They have fought over [the ancient Preah Vihear Temple] so many times, or at least the land surrounding that temple.

"What we saw in February, when many people were also forced to flee their homes, they went to temporary evacuation centres inside schools, inside community buildings, and they stayed there for many days - weeks in some cases.

"Certainly it'll be the same case on the Cambodian side as well," he said.

Indonesian role

The two countries agreed in late February to allow Indonesian observers into the area near Preah Vihear, but the Thai military has since said they are not welcome.

On Friday, Marty Natalegawa, the Indonesian foreign minister, called for the cessation of hostilities between the two countries.

"I call for both sides to resolve their differences through peaceful means," Natalegawa, who is also the chairman of the regional bloc ASEAN, said.

"The use of force has no place in relations among ASEAN member countries."

Kasit Piromoya, the Thai foreign minister, is set to meet Hor Namhong, his Cambodian counterpart, and Natalegawa in Jakarta on Saturday to discuss the terms of reference for the proposal to post Indonesian observers along the disputed area, the Thai state news agency reported.

Thailand recently admitted using controversial Dual Purpose Improved Conventional Munitions during the February fighting but insisted it did not classify them as cluster munitions.

The arms are defined as cluster munitions by the global campaign group Cluster Munition Coalition, which condemned Thailand's use of the weapons.